[Security] SDL2 used in this project is vulnerable

[the-Chain-Warden-thresh]

CVE-2021-33657 is a security vulnerability in SDL2, which is used in this project. The root cause of this CVE is that map which is allocated in Map1toN() or Map1to1 isn't always created as a full 256-entry map. A bmp image can cause heap buffer overflow in Blit1to3(), when the pixel value in pixel array src is equal or larger than the number of colors stored in map. you can easily fix this vulnerability by applying this patch.